Showers are known that are arranged to recirculate water from the shower outflow back to the shower head, so that the water may be reused, and less water is thereby used. Recirculating showers find application principally in portable and mobile applications such as boats and camping vans. For example U.S. Pat. No. 4,828,709 describes a recirculating shower system for use on boats and recreational vehicles. The recirculating water system, which operates with water from a non-mains water supply in the boat or vehicle, comprises filters, a water heater and fresh and used water storage tanks.
In several parts of the world, fresh water is in short supply and measures are taken to preserve the water supply; for example in Western Australia, tax incentives have been introduced to encourage low water use appliances and the installation of some low water use appliances, such as dual flush toilets, is mandatory.
One problem with the use of recirculating showers in domestic applications lies in regulations that require that any water mixed with mains water must meet water purity standards that the waste water from a shower does not meet. In the United Kingdom, such recirculated water must reach Class 2 standard, as defined by the Water Regulations Advisory Scheme: Fluid Category 1 is defined as “Wholesome water supplied by a water undertaker and complying with the requirements of regulations made under section 67 of the Water Industry Act 1991. Example: Water supplied directly from a water undertaker's main”. Fluid Category 2 is defined as “water in fluid category 1 whose aesthetic quality is impaired owing to: (a) a change in its temperature; or (b) the presence of substances or organisms causing a change in its taste, odour or appearance, including water in a hot water distribution system”.
Domestic showers commonly in use are of two general types, namely electric showers and mixer showers.
Typically, electric showers draw water solely from a cold mains supply and heat the water as necessary to the desired temperature. This type of shower therefore does not run out of hot water and is able to provide a stable water temperature. They also have the advantage that they are relatively simple to fit in that they require no special plumbing, only a cold water supply.
The maximum power that can be drawn from a standard domestic electricity supply in the UK is 7.5-11.5 kW, which limits the power that is available to heat up the water as it passes through the shower heater. To get a hot enough shower, it may be necessary to limit the flow rate of the water, typically to a maximum rate of 5-6 litres per minute. Obviously, a higher flow rate could be achieved but only at the expense of providing shower water at a lower temperature. In some parts of the world, this problem is made worse since the maximum power that can be drawn is lower than 7 kW, e.g. in some areas of China, the maximum power that can be drawn is 3 kW, which ultimately can make electric showers unusable due to the extremely low flow rate of heated water.
Electric showers are currently the most common type of domestic shower in the UK market.
Mixer showers achieve the desired water temperature by blending water taken from both hot and cold water supplies using a valve. Mixer showers require both hot and cold water supplies and so obviously require a source of hot water, e.g. a hot water tank or a combination boiler or a multipoint water heater. They therefore require more complicated plumbing than electric showers. In addition, if the water supply is not constant, e.g. because someone else is drawing hot water, the temperature of the shower can fluctuate. However, mixer showers can achieve a higher flow rate than electric showers and are cheaper than electric showers.
Power showers are a variant of mixer showers and include a pump.
Hydrocyclones are known and are mainly used in industrial applications such as in mining (for separating slurries into solids and water), in the field of oil and gas (for the separation of gas from oil/seawater and the separation of oil from seawater) and the paper making industry (for separating out pigments in paper manufacturing). A domestic use of an air cyclone can be seen in Dyson™ vacuum cleaners, which separate dust particles from air. The use of hydrocyclones is also known in central heating systems to remove air bubbles. Hydrocyclones have not previously been applied to shower systems.